Curcumin Inhibits T Follicular Helper Cell Differentiation in Mice with Dextran Sulfate Sodium (DSS)-Induced Colitis

Follicular helper T cells (Tfh) regulate the differentiation of germinal center B cells and maintain humoral immunity. Notably, imbalances in Tfh differentiation often lead to the development of autoimmune diseases, including inflammatory bowel disease (IBD). Curcumin, a natural product derived from Curcuma longa, is effective in relieving IBD in humans and animals, and its mechanisms of immune regulation need further elaboration. In this study, dextran sodium sulfate induced ulcerative colitis in BALB/c mice, and curcumin was administered simultaneously for 7 days. Curcumin effectively upregulated the change rate of mouse weight, colonic length, down-regulated colonic weight, index of colonic weight, colonic damage score and the levels of pro-inflammatory cytokines IL-6, IL-12, IL-23 and TGF-beta 1 in colonic tissues of colitis mice. Importantly, curcumin regulated the differentiation balance of Tfh and their subpopulation in colitis mice; the percentages of Tfh (CD4(+)CXCR5(+)BCL-6(+), CD4(+)CXCR5(+)PD-1(+), CD4(+)CXCR5(+)PD-L1(+), CD4(+)CXCR5(+)ICOS(+)), Tfh17 and Tem-Tfh were downregulated significantly, while CD4(+)CXCR5(+)Blimp-1(+), Tfh1, Tfh10, Tfh21, Tfr, Tcm-Tfh and Tem-GC Tfh were upregulated. In addition, curcumin inhibited the expression of Tfh-related transcription factors BCL-6, p-STAT3, Foxp1, Roquin-1, Roquin-2 and SAP, and significantly upregulated the protein levels of Blimp-1 and STAT3 in colon tissue. In conclusion, curcumin may be effective in alleviating dextran sulfate sodium-induced colitis by regulating Tfh differentiation.